Hi Evhen,
It seems to be a configuration issue in contract account field attribute.
When you are getting this error while opening a contract account, check the contract account category of that (using table FKKVK).
And, then using transaction SM30 open the view V_TFK002A. In that view, check the field grouping configuration of your contract account category. There has to be a discrepancy in that configuration which is resulting to this error.
Hope it helps.
Thanks,
Bodhisattwa